This invention relates to a leveling valve for a vehicle and particularly to a leveling valve for maintaining a constant level of the vehicle chassis relative to its axles in response to unloading and loading conditions.
Leveling valves have been used in the vehicle industry for a number of years. The typical function of a leveling valve is to respond to changes in the vertical relationship between the vehicle chassis and its axles and to compensate therefore by delivering air to or exhausting air from the vehicle's air springs. U.S. Pat. No. 4,379,572 describes and illustrates an air system incorporating one or more leveling valves.
The primary objects of this invention are to provide an air leveling valve that is of simple construction with relatively few parts and components and yet to provide a valve that is positive acting, can be adjusted for speed of response by use of a simple tool, that can be adjusted for duration of open or closed conditions in which air is supplied to or exhausted from the air springs, that can selectively determine the rate of flow or air to and from the air springs, and that has a self-lubricating body.